The impact of preharvest sanitation on the quality and storability of table grapes
PROJECT TITLE: The impact of preharvest sanitation on the quality and storability of table grapes
Project leader: Pieter Louw (ExperiCo)
Contact: pieter@experico.co.za
Duration: 1 November 2022 – 31 December 2024
Problem identification and project objectives:
Table grapes are highly perishable and are often affected by postharvest disorders like berry drop, weight loss, stem browning and fungal decay, most of which are caused by pathogenic fungi. The control of decay on table grapes is becoming increasingly difficult as a result of industry growth, changing weather conditions, increased resistance to fungicides and the introduction of stringent international control measures that limit the use of certain chemicals and residue levels. The most frequently isolated postharvest pathogens of table grapes include Alternaria, Aspergillus, Penicillium, Botrytis and Fusarium (Lorenzini et al. 2012). An increase in decay has been observed when excessive rain is followed by high temperatures. These conditions result in berry cracking (Ramteke et al. 2017) which function as entry and infection sites for pathogens. Opportunistic pathogens such as Alternaria can especially take advantage of these conditions, causing decay and contributing to losses. Control measures during these conditions are therefore critical.
Preharvest vineyard practices such as canopy management and vineyard sanitation play a vital role in reducing and controlling inoculum of pathogens in the vineyard. It also has a significant impact on postharvest quality and storability of table grapes. In some cases, producers are unsure of which practices to follow in order to counter bunch rot when it has already initiated in the vineyard. The physical removal of symptomatic berries from bunches and the vineyard floor can be effective for decay control if applied timeously. Application of biofungicides, biologicals or potential preharvest sanitisers can further aid in reducing decay and alleviating the build-up of fungicide resistance in vineyards (Wang et al. 2019; Romanazzi et al. 2012). This study aims to determine the efficacy of integrated preharvest sanitation practices to improve decay control for the table grape industry.
References
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Ramteke, S.D., Urkude, V., Parhe, S.D. and Bhagwat, S.R. 2017. Berry Cracking; Its Causes and Remedies in Grapes – A Review. Trends in Biosciences. 10(2):549-556.
Romanazzi, G.R., Lichter, A., Gabler, F.M. and Smilanick, J.L. 2012. Recent advances on the use of natural and safe alternatives to conventional methods to control postharvest gray mold of table grapes. Postharvest Biology and Technology. 63(1):141-147.
Wang, J., Wang, H., Zhang, C., Wu, T., Ma, Z. and Chen, Y. 2019. Phospholipid homeostasis plays an important role in fungal development, fungicide resistance and virulence in Fusarium graminearum. Phytopathology Research. 1(16). doi.org/10.1186/s42483-019-0023-9